1. Field of the Invention
The present invention relates to conductive metal particles, conductive composite metal particles and applied products using these metal particles.
2. Description of the Background Art
In an electric and electronic field, conductive materials containing conductive particles in an insulating organic material have heretofore been widely used for the purpose of achieving electrical connection between circuit devices and electrical connection between wirings in a circuit device.
In mounting of electronic parts on semiconductor integrated circuit boards or the like, for example, surface mounting and COB (chip on board) are utilized for the purpose of mounting electronic parts on a printed circuit board at a high density. In such a mounting method, a conductive adhesive in the form of paste or a film, which contains conductive particles, is used (see Japanese Patent Application Laid-Open Nos. 84716/1985, 231889/1988, 259766/1992 and 75250/1993, etc.).
An anisotropically conductive sheet containing conductive particles in an elastomer is used as a connector for achieving electrical connection between circuit devices, for example, a printed circuit board and a leadless chip carrier, liquid crystal panel or the like. Further, in electrical inspection of a circuit device such as a printed circuit board or semiconductor integrated circuit, it is conducted to intervene an anisotropically conductive sheet between an electrode region to be inspected of the circuit device, which is an inspection target, and an electrode region for inspection, of a circuit board for inspection in order to achieve electrical connection between electrodes to be inspected formed on a surface of the circuit device to be inspected and electrodes for inspection formed on the surface of the circuit board for inspection.
As such an anisotropically conductive sheet, there have heretofore been known those of various structures. For example, those obtained by uniformly dispersing metal particles in an elastomer (see Japanese Patent Application Laid-Open No. 93393/1976), those obtained by unevenly distributing particles of a conductive magnetic material in an elastomer to form many conductive path-forming parts extending in the thickness-wise direction thereof and insulating part for mutually insulating them (see Japanese Patent Application Laid-Open No. 147772/1978, etc.), and those with a difference in level defined between the surface of a conductive path-forming part and an insulating part (see Japanese Patent Application Laid-Open No. 250906/1986, etc.) are known.
Further, in double-side printed circuit boards in which wiring layers are formed on both sides of an insulating layer and multi-layer printed circuit boards in which a plurality of insulating layers and a plurality of wiring layers are alternately laminated, columnar conductive materials with conductive particles contained in a curable resin have been used in recent years, in place of plated through-holes (via-holes) as a means for conducting electrical connection between the wiring layers (see Japanese Patent Application Laid-Open Nos. 255982/1996 and 256687/1998, etc.). Since such a conductive material may be formed by filling a conductive paste composition, in which conductive particles are dispersed in a liquid thermosetting resin, into through-holes bored in an insulating layer, and subjecting the conductive paste composition to a curing treatment, electrical connection between wiring layers can be achieved through simple steps, and moreover circuit boards high in connection reliability can be provided because none of chemicals such as a plating solution are used.
In such conductive materials as described above, composite metal particles obtained by plating the surfaces of particles of a metal, for example, nickel, copper or the like with gold high in conductivity and chemically stable are preferably used as the conductive particles.
Such conductive particles are required to provide conductive materials having stable conductivity, specifically to provide conductive materials which have high conductivity and are high in reproductivity thereof. Therefore, conductive particles whose average particle diameter and particle diameter distribution fall within respective particular ranges are used in the production of conductive materials.
However, it has been found that the mere use of conductive particles whose average particle diameter and particle diameter distribution fall within respective particular ranges fails to provide any conductive material having stable conductivity.
The present invention has been made on the basis of the foregoing circumstances and the first object of the present invention is to provide conductive metal particles and conductive composite metal particles by which conductive materials having stable conductivity can be provided.
The second object of the present invention is to provide a conductive paste composition which has high conductivity and is high in reproductivity thereof.
The third object of the present invention is to provide a conductive sheet which has high conductivity and is high in reproductivity thereof.
The fourth object of the present invention is to provide a circuit board which has high conductivity between wiring layers thereof and is high in reproductivity thereof and moreover high in connection reliability.
The fifth object of the present invention is to provide a conductive connection structure by which electrical connection high in conductivity and high in reproductivity thereof can be achieved.
The sixth object of the present invention is to provide an electrical inspection apparatus for circuit devices, by which electrical connection high in conductivity and high in reproductivity thereof can be achieved to a circuit device which is an inspection target.
According to the present invention, there are provided conductive metal particles having a number average particle diameter of 5 to 100 xcexcm, a BET specific surface area of 0.01xc3x97103 to 0.7xc3x97103 m2/kg, a sulfur element content of at most 0.1% by mass, an oxygen element content of at most 0.5% by mass and a carbon element content of at most 0.1% by mass.
In the conductive metal particles according to the present invention, the coefficient of variation of the particle diameter may be preferably at most 50%.
The saturation magnetization thereof may be preferably at least 0.1 Wb/m2.
According to the present invention, there are also provided conductive composite metal particles obtained by coating the surfaces of the conductive metal particles described above with a high-conductive metal.
In the conductive composite metal particles according to the present invention, the thickness t of the coating layer of the high-conductive metal, which is calculated out in accordance with the following numerical expression, may be preferably at least 10 nm:
t=[1/(Swxc2x7xcfx81)]xc3x97[N/(1xe2x88x92N)]
wherein t is the thickness (m) of the coating layer of the high-conductive metal, Sw is the BET specific surface area (m2/kg) of the conductive metal particles, xcfx81 is a specific gravity (kg/m3) of the high-conductive metal, and N is a ratio of a weight of the coating layer of the high-conductive metal to a weight of the conductive composite metal particles.
In the conductive composite metal particles according to the present invention, the high-conductive metal may be preferably gold.
The content of the high-conductive metal in each surface layer portion of the conductive composite metal particles may be preferably at least 50% by mass.
The BET specific surface area of the conductive composite metal particles may be preferably 0.01xc3x97103 to 0.7xc3x97103 m2/kg.
In the conductive composite metal particles obtained by coating the surfaces of the conductive metal particles whose saturation magnetization is at least 0.1 Wb/m2 with the high-conductive metal, the electric resistance value R as measured in the following manner may be preferably at most 1 xcexa9:
Electric Resistance Value R
A paste composition is prepared by kneading 0.6 g of the conductive composite metal particles with 0.8 g of liquid rubber, the paste composition is arranged between a pair of electrodes each having a diameter of 1 mm and arranged so as to be opposed to each other at a clearance of 0.5 mm, a magnetic field of 0.3 T is applied to this pair of electrodes, and the pair of electrodes are left to stand in this state until the electric resistance value between the pair of electrodes is stabilized, thereby measuring an electric resistance value at this time.
According to the present invention, there is further provided a conductive paste composition comprising the conductive metal particles and/or conductive composite metal particles described above.
According to the present invention, there is still further provided a conductive sheet comprising the conductive metal particles and/or conductive composite metal particles described above in an organic polymeric substance.
According to the present invention, there is yet still further provided a circuit board comprising a conductor containing the conductive metal particles and/or conductive composite metal particles described above in an organic polymeric substance.
According to the present invention, there is yet still further provided a conductive connection structure connected by the conductive paste composition described above.
According to the present invention, there is yet still further provided a conductive connection structure connected through the conductive sheet described above.
According to the present invention, there is yet still further provided an electrical inspection apparatus for circuit devices, comprising the conductive sheet described above, wherein electrical connection to electrodes to be inspected of a circuit device to be inspected is achieved through the conductive sheet.